A conventional refrigeration cycle device includes a compressor, a condenser, a decompressor, and an evaporator, and a refrigeration cycle is formed by connecting the components via a refrigerant pipe. In general, in a refrigeration cycle device adopting a zeotropic refrigerant mixture, since the boiling points of refrigerants contained in the zeotropic refrigerant mixture are different from one another, the composition of the circulating refrigerant may change. In particular, in the case where the refrigeration cycle device has a large scale, a significant change in the refrigerant composition occurs. That is, when the refrigerant composition changes, even under the same pressure condition, there is a possibility that the condensing temperature or the evaporating temperature may change. In the case where the refrigerant composition changes, an appropriate refrigerant saturation temperature cannot be obtained in a heat exchanger. Thus, it becomes difficult for the refrigerant to condense and liquefy or to evaporate and gasify in the heat exchanger. As a result, there is a possibility that the heat exchange efficiency may reduce.
Furthermore, when the refrigerant composition changes, even if the refrigerant outflow side of the heat exchanger has the same temperature and the same pressure, there is a possibility that the degrees of superheat and subcooling may change. That is, since an adequate degree of superheat is not achieved before suction into the compressor, a liquid refrigerant flows into the compressor. Since the density per volume of a liquid refrigerant is higher than that of a gas refrigerant, when the compressor is about to compress the liquid refrigerant, an excess driving torque is applied to the compressor. Thus, the compressor may be damaged by the application of such an excess torque.
Furthermore, since an adequate degree of subcooling is not achieved before flowing into an expansion valve, the refrigerant may turn into a two-phase gas-liquid refrigerant. As a result, there is a possibility that refrigerant noise may occur at the expansion valve or an instability phenomenon of the refrigerant may occur.
Therefore, as a configuration for reducing the variation range of a refrigerant composition circulating in a refrigeration cycle device, a refrigeration cycle device which includes a refrigerant reservoir on a high-pressure side (for example, a receiver) is known. The variation range of a refrigerant composition circulating in the refrigeration cycle device is smaller in a refrigeration cycle device of the aforementioned type than in a refrigeration cycle device which includes a refrigerant reservoir on a low-pressure side (for example, an accumulator).
However, even with such a configuration, if refrigerant leakage occurs in the refrigeration cycle, the variation range of the refrigerant composition will increase, irrespective of whether the refrigerant reservoir is arranged on the low-pressure side or the refrigerant reservoir is arranged on the high-pressure side. This means, on the contrary, that refrigerant leakage can be detected by detecting a variation in the refrigerant composition.
Therefore, as a conventional refrigeration cycle device that includes means for detecting a refrigerant composition in order to suppress a reduction in heat exchange efficiency, avoid damage to a compressor, suppress generation of a refrigerant sound, suppress an instability phenomenon, and detect refrigerant leakage, the following configuration has been available. That is, in the conventional refrigeration cycle device, a bypass which is connected so as to allow bypassing of the compressor is formed, and the bypass includes a double-pipe heat exchanger and a capillary. The refrigeration cycle device detects the refrigerant inflow-side temperature of the capillary, the refrigerant outflow-side temperature of the capillary, and the refrigerant outflow-side pressure of the capillary, and calculates the refrigerant composition based on the detection results. Moreover, some of such refrigeration cycle devices include a bypass which allows bypassing of the compressor. In the bypass, a double-pipe heat exchanger and a capillary are connected. A temperature sensor is provided on the inlet side of the capillary, and a temperature sensor different from the temperature sensor provided on the inlet side and a pressure sensor are provided on the outlet side of the capillary.
Such a refrigeration cycle device obtains the refrigerant composition by circulating a zeotropic refrigerant mixture in the refrigeration cycle, detecting the temperatures and pressure of the zeotropic refrigerant mixture with the two temperature sensors and the pressure sensor described above, and identifying the detected temperatures and pressure with a composition relational expression of the refrigerant (see, for example, Patent Literature 1).
Furthermore, a conventional refrigeration cycle device includes a compressor, a four-way valve, a condenser, an expansion valve, and an evaporator, which are connected via a refrigerant pipe to form a refrigeration cycle. Moreover, some of such refrigeration cycle devices include a suction pressure sensor and a suction temperature sensor that are included in a suction pipe of a compressor, and detect the pressure of a refrigerant circuit on a low pressure side and the refrigerant temperature of the suction pipe (see, for example, Patent Literature 2).
The refrigeration cycle device of Patent Literature 2 calculates saturation pressure based on the refrigerant temperature detected by the suction temperature sensor, and corrects an output value of the suction pressure sensor based on a deviation of the pressure detected by the suction pressure sensor with respect to the saturation pressure.